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تسجيل مستخدم جديدObscured clusters.I. GLIMPSE30 - Young Milky Way Star Cluster Hosting Wolf-Rayet Stars
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R. Kurtev
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Young massive clusters are perfect astrophysical laboratories for study of massive stars. Clusters with Wolf-Rayet (WR) stars are of special importance, since this enables us to study a coeval WR population at a uniform metallicity and known age. GLIMPSE30 (G30) is one of them. The cluster is situated near the Galactic plane (l=298.756deg, b=-0.408deg) and we aimed to determine its physical parameters and to investigate its high-mass stellar content and especially WR stars. Our analysis is based on SOFI/NTT JsHKs imaging and low resolution (R~2000) spectroscopy of the brightest cluster members in the K atmospheric window. For the age determination we applied isochrone fits for MS and Pre-MS stars. We derived stellar parameters of the WR stars candidates using a full nonLTE modeling of the observed spectra. Using a variety of techniques we found that G30 is very young cluster, with age t~4Myr. The cluster is located in Carina spiral arm, it is deeply embedded in dust and suffers reddening of Av~10.5+-1.1mag. The distance to the object is d=7.2+-0.9kpc. The mass of the cluster members down to 2.35Msol is ~1600Msol. Clusters MF for the mass range of 5.6 to 31.6Msol shows a slope of Gamma=-1.01+-0.03. The total mass of the cluster obtained by this MF down to 1Msol is about 3x10^3Msol. The spectral analysis and the models allow us to conclude that in G30 are at least one Ofpe/WN and two WR stars. The WR stars are of WN6-7 hydrogen rich type with progenitor masses more than 60Msol. G30 is a new member of the exquisite family of young Galactic clusters, hosting WR stars. It is a factor of two to three less massive than some of the youngest super-massive star clusters like Arches, Quintuplet and Central cluster and is their smaller analog.
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ry. When beginning our WR searches using infrared techniques it was not clear whether WR number predictions were too optimistic or whether there was more hidden behind interstellar and circumstellar extinction. During the last decade we pioneered a technique of exploiting the near- and mid-infrared continuum colours for individual point sources provided by large-format surveys of the Galaxy, including 2MASS and Spitzer/GLIMPSE, to pierce through the dust and reveal newly discovered WR stars throughout the Galactic Plane. The key item to the colour discrimination is via the characteristic infrared spectral index produced by the strong winds of the WR stars, combined with dust extinction, which place WR stars in a relatively depopulated area of infrared colour-colour diagrams. The use of the Spitzer/GLIMPSE 8$mu$m and, more recently, WISE 22$mu$m fluxes together with cross-referencing with X-ray measurements in selected Galactic regions have enabled improved candidate lists that increased our confirmation success rate, achieved via follow-up infrared and optical spectroscopy. To date a total of 102 new WR stars have been found with many more candidates still available for follow-up. This constitutes an addition of $sim$16% to the current inventory of 642 Galactic WR stars. In this talk we review our methods and provide some new results and a preliminary review of their stellar and interstellar medium environments. We provide a roadmap for the future of this search, including statistical modeling, and what we can add to star formation and high mass star evolution studies.
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